Field of the Disclosure
Embodiments of the present disclosure generally relate to non-volatile memory, and more specifically, embodiments disclosed herein relate to storing multiple bits in a non-volatile memory cell and adjusting the size and/or shape of the multiple bits.
Description of the Related Art
A number of different memory technologies exist today for storing information for use in computing systems. These different memory technologies may, in general, be split into two major categories, volatile memory and non-volatile memory. Volatile memory may generally refer to types of computer memory that requires power in order to retain stored data. Non-volatile memory, on the other hand, may generally refer to types of computer memory that do not require power in order to retain stored data. Examples of types of volatile memory include certain types of random access memory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM). Examples of types of non-volatile memory include read-only memory (ROM), flash memory, such as NOR and NAND flash, etc.
In recent years, there has been a demand for higher density (capacity) devices, which have relatively low cost per bit, for use in high capacity storage applications. Today, the memory technologies that generally dominate the computing industry are DRAM and NAND flash; however, these memory technologies may not be able to address the current and future capacity demands of next generation computing systems.
Recently, a number of emerging technologies have drawn increasing attention as potential contenders for the next generation memory type. Some of these emerging technologies include phase change memory (PCM), resistive RAM (known by both the acronym ReRAM or RRAM) and others. For the sake of convenience, resistive RAM may be referred to as ReRAM throughout the present disclosure.
PCM is a type of non-volatile memory technology that functions based upon switching a memory cell, typically based on chalcogenides such as Ge2Sb2Te5, between two stable states, a crystalline state and an amorphous state. Switching between the two states may be enabled by heating the memory cell, which is typically done by applying an electrical current through the PCM cell. ReRAM, which shares some similarities to PCM in that they both operate via mechanisms that have state-dependent resistance, is also a type of non-volatile memory technology that generally stores data using changes in electrical resistance.
Each of these different emerging memory technologies may be serious contenders to dislodge NOR and NAND flash memory in solid state storage applications and, in the case of NAND flash, solid-state drives (SSDs). As such, it may be desirable to provide techniques that may be used to achieve higher capacity in non-volatile memory while minimizing cost per bit.